1. Technical Field
The present invention relates in general to data communication and, in particular, to improving bandwidth availability in a data communication network. Still more particularly, the present invention relates to a method and system for improving bandwidth availability in a data communication network by tokenizing messages.
2. Description of the Related Art
Currently, there is great interest in leveraging the existing Internet infrastructure, protocols, and bandwidth to provide additional services beyond conventional data communication between computers. One area of particular interest is IP (Internet Protocol) telephony. In order to support IP telephony, two signaling standards have emerged, the H.323 protocol suite developed by ITU-T (International Telecommunication Union) and the Session Initiation Protocol (SIP) developed by the IETF (Internet Engineering Task Force). Both of these signaling protocols provide mechanisms for call establishment and teardown, call control and supplementary services, and capability exchange.
During VolP (Voice over IP) call establishment, several control and set-up messages are exchanged before and/or during a call. These messages are similar in function for SIP and H.323, but very different in their formats. In particular, SIP messages are in text-based (using ISO 10646 in UTF-8 encoding), while H.323 messages are encoded utilizing ASN.1 PER (Packed Encoding Rules). The PER-encoded H.323 messages are more compact and therefore optimal for storage; however, they consume more CPU processing cycles than SIP text messages because of the need to encode and decode the messages. In contrast, the SIP messages, being text, are efficient in terms of processing cycles, but do not make as efficient use of storage or the bandwidth of communication links, such as the mobile-to-base station air interface or dial-up modem connections, which are characterized by low bandwidth and high error rates.
Consequently, the present invention includes a recognition that it would be desirable to reduce the sizes of SIP messages to better utilize low bandwidth connections in data communication networks.
Although shorter SIP messages can be obtained, for example, by directly applying standard LZ77 (Lempel-Ziv 1977) schemes such as gzip or winzip, processor-intensive compression and decompression cycles would be required as for PER-encoded H.323. Because consuming processor resources to directly compress textual SIP messages is viewed as undesirable, the present invention applies simple tokenization to certain terms and fields in a SIP message to produce a compact tokenized message that is up to 30% smaller than the original message. Thereafter, the tokenized messages can optionally be compressed further utilizing a standard compression algorithm, such as LZ77, to attain a substantial compression ratio. Applying a standard compression scheme, such as LZ77, after tokenization can decrease the SIP message size by an additional 10%.
All objects, features, and advantages of the present invention will become apparent in the following detailed written description.